Outboard motor assembly



OUTBOARD MOTOR AS SEMBLY 2 Sheets-Sheet 1 original Filed Feb. 4. 1929 Y.75 3y Q95@ f M2 Sept. 22, 1931. L. J. JoHNsN E1 AL 1,824,738

GUTLBA'RD MTR ASSMBLY origina md m. 4. mais a shewsnm z 1534 lkl IW Jlill/lill ,/WE/vonf Lou/5 J JOHNSON. .HH/mr L, JUHNSo/V,

IZ y wm QW @f5 Patented Sept.- 22,' 1931 LOUIS J. .IonNsoiv'hn'n"L.,.IonivfsoN, or WAUKEGAN, rLLiNoIsnssIG-Nonsl 'To JOHNSON,imo'riinns ENGINEERING `conrroinrrrjoiv',

Appneaticn sied 'February si;` 1929," serial No.Y 337,244.v y "ireewa-Apriiis 193i.V

invention relates topropulsion devices lchamber..into which theexhaustgases from for: water vehicles 'and incre-A particularly to .a type ofdevicecoinmonly :known'as .an oi-ithoard motor, which -is-.aselfeontained unit i* includingthecomplete gasoline driven power @plantand propelleryadapted ior bodily at- 'liso In the present outboardtachmentto a water-` vehiclejk `VVhile for-pur-` poses of'exemplification, the inventionfisl il- -liistratedvas applied -tohanoutboard'inotor `'io` type of device, it llisto begundeistood that it isalso applicable to similar constructions of theinboard motor type. A .ij Y motor art, the propulsion of the water vehicle .at high speeds isvery desirable. The object offou-rpresent invention is to providefanaoutboard or inboard inotor type of device .which ,will producerelatively high rates. otpropulsionjof. the

`Water vehicle through. the water and which will eliminate theobjectionab'lenoises and odors incident tothe. discharge-ot thecylinder; exhaustv gases :while not interfering with the facileystartinglofthe inotor audits running :at comparatively lowfspeeds whileat the saine 4time not interferingv with; the proper turning ofthe lowerunit ofrtjhedevice for Other objects of our invention are to provide asimple, unitary` construction `of out'- board `or inboard type oflinotor which utilizes the'tubular housing surrounding the verticallydepending drive shaft running to the .propeller as a 'meansforconducting the cylinder exhaust gases -from the'engine .cyl-

inders downwardlyy ,and .discharging them below normal .water` levelwherebytol eliminate noise and smell'andalso for, utilizing this tubularycasing. as a means for conducting cooling wateriroinY the of water-.inwhich the, propeller carrying casing isiniinersed,upwardlyto the waterjacket of the engine and thence downwardly: kvagain throughthetubuflarhousing, dischargingthe saine below normal waterlevel and a inanner suchthat thisfcooling .waterI assists ein cooling, the-.hot exhaiistgaseswhich are likewise conducted through' thi s` tubular casing. Stillanother oblect of our invention resides in providing .a constructionwherein there .the cylinder are. discharged',Y which expanl* 1,824,758yf OililsoUTH. BEND, rNnrniIfL,A A o sion chamber also acts asamuiflerand in discharging' the Vexhaust gases'` from this.y ex- .pansionchamber into the tubularcasing sur- 1 .throughv suitable passage-waysforinecll 'integrallyin the Vlowercasing and preferably in .f

.the anti-cavitationplate so asto discharge .these eirhaiitst Agases*underwater.` 'A Y further ob]ect of this aspect of our invention residesin providing the vexpansion chamber or inutlier with a water jacket Vandin Vproviding ineansv for conducting? cooling 'water'upwardly throughthe .hollow casing into the water jacket of theengine cylinder, thenceinto, tlie..vwater-jacket for; the e-Xpai'isionichainber and thencedownwardly through thehollow casing to ay point of dischargelocatedbelow normal water levelwhereby during-.tlfie g propulsion of thedevice', water will Inotonly ycool the 'engine cyl indes:r the expansionich'ainbcr .or inufiier,y but Ywill also lserve tok cool the exhaustgases discharging adcfiwnwardly through. the hollow casing .and willserve to prevent over-heating of the vertically deypending drive shaftand the tubular casing.

. Another object of our invention resides in "the construction andarrangement of an underwater exhaust for the engine cyliders asan-integralpartof the anti-cavitation plate, preferably formed integralwiththe propeller carrying casing, and. for constructing :the same withintegr-al passages connecting with Vthe tubular casing siurouridin'g'the vertically depending drive shafhand l which I turnconnects with theexpansion chamber .or muierleading to the engine `cylinder eX- haustwhereby the hot gases are discharged at the rear of the propellerandwithout inte/r- Ateringvvit-h the proper propulsion oft-he device onitsturningor .steering orV reversing.

, Stillanotherobjcct of vour invention resides i inthe-provision of thistype of 1device wherein the lower. propeller carrying unit isof 'entirestreainline' construction andY wherein fthe antifcavitation plateoverlying the propeller is provided on its upper' "portion with,

iooV

structure shown in Figure 1 at right angles bular casing surrounding theengine drive eliminatingconcomitant noises and objection- .Figure 4 visan enlarged view of aportion ofthe inechanismfor controlling theopening` -and closing ofthe underwater exhaust rean internal passageconnecting with the tushaft and in turn connected with thecylinder'exhaust gases so as to permit the proper turning movement ofthe vstream-line. structure for steering and /or reversing, whilepermitting the underwater discharge ofthe eX- Alia-ust gases. v

'"Tn general, the obj ects of our invention are.v `toi vmaintain thesubstantially 4completed streain-line formation of this lower propellercarrying unit which is submerged in the water while permitting thebodily turning of this structure for steering and/or Vrrevers- 1 ing,while at the saine time utilizing this structure and particularly theanti-cavitat-io'n portion thereof and thet'ubular housing connectedI tothe upper portion of this structure' as a means for conductingthecylinder eX- -haust gases to a point below normal water level,thereby permitting high speeds-and able exhaust gas odors. @These andother vobjects of our invention willbe apparent from a perusal of thefollowing specification when taken in connection with the accompanyingdrawings, wherein: yr. Y

Figure 1 is a sectional side view of one form ofour new invention;

Figure 2 is al section 'on line 2-2 thereof;

Figure Sis a section on liii`e`8--3 of Figurel; 1

lief;

Figure is perspective rear view of the thereto with certainportionsbroken -away tosliow the underwater exhaustv relief;

' Figure 6 isa section on line 6-6-of Figure Figure 7 isasection 1;fand

FigureS is a. section on ure rv1.V f

Referring now to the drawings in detail, as beforeexplained, ourinventionis exemplitied in connection with an outboard `motorconstruction which includes as a type of powerplant or prime mover, thedouble opposed two-cycle internal combustion engine 2 having the usualvertically depending drive shaft 4 connected thereto andincluding -acrank casing 6 upon the upper end of which is mounted an extension `ofthe engine drive shaft so asto include the usual fly-wheel magn eto 8starter andother construction commonly present in outboard motorvconstruconzline 7-'7 ofFigure line 8-8 of Fig- -tion', ,-including alsothe usual advance' and retarding handle 1 0 of the magneto.

viding the Vengine cylinders 2 with the usual of the cylinders with alateral extension 12 vwhich as shown in Figure 1, forms a relativelylarge expansion chamber 14. This enpansion chamber also acts as amufiier. This extension 12 is provided with:V internal passagessurrounding the expansion chamber 14 which passages 16 provide a waterjacket for is provided with a depending tubular housing 22 suitablyattacliedtoiftlie casingso as to form a gas-tight and water-tight Jointthereto; f vThis tubular easing'A 22v conoentrically Vsurrounds' thevertically depending power drive shaft "f4 throughout its flength; AThistubular-casing 22 is mounted' for rotary ymowement in Ythe usual'stationary collar or bearing 24, which, in turnyis'carried bythe usualsame may be attached tothe iusual outboard motor as is wellknown in theart, it-'being understood tliat"'the 'tubular housing 22 'is rotatablewithin this'sle'eve'l24 about the' depending Vdrive shaft 4'asan axis.The lower end of the'tubularho'using 22 is rigidly and detachablyconnectedto'the propeller carrying housing or lower unit. It will beunderstood that this lower unit is the portionvthat is normally'submergedfin the'body of water inl which thefwaten vehicle orvcraftrests so Vthat theV propeller carried bythis lower unit will propeltheboat .through the water.

order to carry-out the objectsof our invention, we lhaveffojrmed thelower unit for propeller carrying'c'asing of entire stream- 'line"'contour. 'While this casing may be lintegrally made, wezp'refer to formit of ainain portion 30 which extends vertically upwardly so as to berigidly bolted as at V32 and 34 with thejlower' portion of the tubular'casing 22" and we provide the lower portion 36 of this unitwhichfcarries the'usual"ijiropeller shaft-"38 and4 propeller 40 and askeg 42 as a 4separate casting, the samebeing rigidly secured by meansv'of bolt-s 32, if desired,f to the portion 30 and tubular casing 22.The casting 80 is'provided with aV central bore 442 through which passesan extension shaft 46 fof the propeller drive shaft4. j This shaft 46hason its klower-end a bevel gear 48 meshing lwith-another bevel gear50'ontherusual pro- `peller drive shaft 38.,l The. junction of theextension shaft"46 ai1d"the drive shaft v4 is effected 'by'means ofsuitable coupling 50.

Referring to the tubular housing 22,'it will be seen that the'sameincludes a tubular wall ways 54'and 56'formedfby integrally cast` walls,if idesired. v@The `passagey 54 is adapted t t l l l 'toconduct'cooling'wa'ter,upwardly while the yPe of 111111311213 We form the crank@afsllg passage 56 -is Vadapted;toconvey the cooling l '52'whichconcentrically' surrou'ndsfthe drive 1"125 water coming from thecylinder'j-acket and inuiiler downwardly. f Inaddition, thetubula'rhousing 22 provides relatively-large vertically extending passage-ways"58 randA 60,

which almost entirely surround thepassage iways 52, 54and 56.Tliese-passage-waysS and 60 are for the conduction of the cylinder`ekhaust gases downwardly 4through the'tubular casing 22;

'At' its upper portion, thisvtubularcasing 22 is provided with apreferably integral-lat- 'connects with a'lange 66 surrounding Vanopening 68 in theexpaiision chamber orinuflier 14 so that cylinderexhaust gases will be discharged through this expansionchan'iber throughthe neck 64 into the hollow tubular casing 22.- The vupper portion ofthe tubular passage 54 registers withlv apassage-way 70 in the lowerportion of the crank casing and this passage 70 is formed as asubstantially hollow collar 7 2 which has` an outlet connecting to apipe 74 which in turnl connects with the lower portion of the waterjacketof each cylinder. There are two orV more of these pipes 74`eachconnecting yto the lower portion of the jacket of each cylinder. j j lnaddition, the upper portion oi' each cylinder jacket connects 'i'vithaYipe 7 6 which `in turn empties' intoV a neck (8connecting with jacket16.;l Theupper portion of this jacket, 'i as shown in Figure 1,V isprovided with a'conne'ction with across pipe80 which passessubstantially`diaiiietrically through the expansion chamber 14 and connects with apipe 82 which passesaround atubiilar' housing as at 84andconnects withinternal passage 56 of the tubular housing so that the heated waterafter passi-ng `through the engine cylinder jacketand the expansionjack-v ets 16, will be conducted outwardly and downwardly through thispassage56. y v .j

v The lower portion of the'tubular housing or casing 22 is providedwithalateraland integrally projecting portion 82 which forms, aninternal passage 84 communicating with the exhaust passages 58 and 60.`In likeY manner, the lower housing section 30 is provided withanintegrally cast anti-cavitation plate 86." The upper portion ofthissection 30 is formed integral with' the anti-'cavitation plate 86 asshown clearly iny Figures 1, Sand 5, the portion 88 of Athis sectiondirectly above the anti-cavitation plate being extended laterally orviewing Figui'el, rearwardly, and merging in stream-line contour intothis anti-cavitataion plate. This portion 188 is substantiallynarrow andis inore'or less t'ubular to provide an A,internal passage-way 90 whichconnects withcthe internal passageway 84'of the portion Y82, on thehollow tubu- `lar housing vso as to receivevthe flow of the eX- flow theplane 'ofthelantil-cavitation plate'86 at whiclifpoint it is formedas lav rearwardly extending nozzle 90. of substantially narrow` "dimensionsbeingcpreiierably of theshapeq 'j shown in yFigure 5,v lfor discharging:the eX- L haust gases underwater; The bottom portion ofrthisfnozzle 90is formed asa substan- :tially v'horizontal-plate or ledge 92 whichaslsists'in/deliectingtlie exhaust gases outwardand rearwardly. Thea'nti-cavitatioiiC plate ovcrhangs the nozzle 90 at the pointl94.

v'It-will' beunderstood, ofcourse, that the normal water line is wellabove the anti-cavitationplate, being substantially half-way be- H ntween the upper-most part of the anti-cavitation plate86 andthejunctionbetweenthe section 30 'and-the tubular housing-22v so that theexhaustiiozzlev 90 iss'ubmerged inwater at all t'iines du ringzthepropulsion of the boat.- n :In addition, this section 30 of thelower'hous-"-c ing is providedwith an internal passage 96 former has anupper opening registering with andanadditional internal passa'gefdfv Thethe passage 5.4in the tubularhousing and the latter has anV openingregistering withthet passage 8611i the tubularhousing. The in- 'ternal,passage 96 terminates in a water gathimY ering mouth 100 which liessubstantiallyrad-` jacent to and directly in the rear of the path j oftraveloi the propeller blades'102as they lare revolved by the source ofpower. 1 Suit- 'a'ble bars 104 are placed across the mouth of this waterintake 100 to prevent the vingress of? dbris. In a siinilar'inanner thesection'30 is vvprovidedk with a water'dscharge nozzle 106 whichcommunicates with the passage-way flowing around on all sides of thepassageway'44 through which thev extension drive shaft 46 passes.'yVThis dischargev passage 106 :lies closely adjacent to and directly infrontYV l'ofthe path of travel of the propeller blades i 102. Iftwill beseen by this construction'that thelower casing section 30`-closelyarches over the-path'of travel ofY the propeller blades so tliat'thewater gathering mouth and water discharge -moutliare placedsubstantially 'olose'to this zone oftravel.

that in starting `or running at low speeds these exhaust gases will notbe discharged below normal water level', but will be dischargeddirectly` into the air, thereby preventing the creation of an exhaustback pressure in the cylinders; One embodiment of this means consistsiny providing the tubular casing 22 with an exhausty outlet 108 wellabove normal water level, This outlet is normally closed by a valve 110and byrmeans of a coil spring 112. The valve is pivoted at -v114 and isop-4 eratedby means of a lever 116 and a pivoted rod'118 lInorder,toprovidefor a suitable adjustment, there. is.4 a.- screw 120 passing'through the stem o'the valve between it and its pivot114`, which screwis engaged by the doo ics

12el I Verable from ythe outboard'inotor.

shortlever' 116. The rod 118 iszadapted to bevoperated by any typeofspeed control op- In vthe presentinstance, it is operated by means ofthe magneto advance and retarding lever shown and claimed in our priorapplication,

-Serial No. 385,447; briefly stated, there v'is a sector 122 onthemagneto plate provided with shifted in one direction or the other,-the rod 118 will be correspondingly operated to open or close the valve110, the arrangement being that when the magneto .is retarded for low,speeds the .valve `will be 'opened to permit the direct discharge ofthe exhaust gases into the air,'whereas when the magnetocontrol isextending shifted'for high speeds the valve will be closed andv theexhaust gases will be discharged through the passages 90 and below thenormal water level. It is obvious that instead of having a magnetocontrol vthat this control :may beoperated from any other'automati-Acally operated portion of the motor.

lt will be apparent .from the foregoing that in the operation of themotor, when the boat is being propelled by reason of the propeller 14:0,the pressure thereof will pump or kforce water into the water gatheringmouth 100, thence4v Vupward-ly"through passage 96 then through passage54, thence through opening 70, thence through water pipe 74 into thewater jacket ofthe engine', thence from' the top ofthe vwater jacketthrough pipe 76into the water jacket of the expansion chamber ormanifold from which the .heated water flows tothe water where it isdrawn directly j, therefrom downwardly through pipe 80 which pipepasses, through the manifold-and'thence outwardly through -pipe 82across-to passage 56, thence downwardly through passageway 98 to thewater Vdischarge mouth 106 at which point the'rotation of the bladeswill serve to assist the cir-. culation by lsucking the samerfrom t-hemouth 106. lt will also be appreciated that during the Yforward travelof the boat, the rush of the water will also serve to force water intothe mouth 100`and will also serveto suck water from the mouth 106. At.the same time,'the exhaust gases from the cylinder will fill theexpansion "chamber and muffler and will then flow through opening 68into the tubular housing where the exhaust gases Vlrwill pass downwardlythrough the wide pas- ',sages 58 and G0 to the bottom of the housingwhere they will pass into the rearwardly hollow portion 82 and passthrough the conduit Stthereof downwardly and will dischargerearwardlybeneath the anti-cavitation plate 8,6 and to the rear of the.propeller 40. AtV this point due to the f 3ro nilsion of the lowercasing forwardl and dueto'the re-activelforce of the propeller,

'suction will be created directlyopposite the Vmouth 94eA so as toassist in the ejection of theseexhaust gases. These gases willdisvcharge.rearwardly well within the stream line of 'the underwaterhousing and will as-.Z

sistinl preventing the possibility of air being peller. l Thisisespecially so since the force of expulsion of the gases creates a moreorless solid discharge mass of gases .and pari175 ticularly so due to thepresence of the plate 92.' `lt willbe noted that the exhaust mouth isprovided with laterally projecting Ywings' on each side thereofwhich'serve to kdeflect the water into the water gathering Vmouth andseparate this zonefrom the exhaust gas Zone. During the Adownwardkdischarge of the'exhaust gases through this underwater exhaust, it willbe notedv that the exhaust gases are constantly being cooled by Tr theupwardly .and downwardly flowing column of cooling water on their way toand from the water jacket of the engine and the rwater, jacket of theexpansion chamber.

It is to be particularly borne inA mind that unit is stream' line soasrtocut downto the minimum the frictional resistance as it passesthrough `the water. 1tthe'same time, the vcooling water is withdrawnfrom the bodyof drawn downwardly-into the race of the pro- 'T his is dueto the fact that this entire lower 00 water'in whichthe housing isimmersed and Q05 takenv up tothe water jacket and is also broughtdownwardly again Vand Adischarged into thestream line construction.Furthermore, it will be noticed that by reason of our manner ofdischarging the exhaust from the cylinders beneath the water and wellwithin the stream-liney contour of this lower structure and beneath theanti-cavitation plate, we have cut down frictional resistance to theminimum. This is brought about by the utilization of the round tubularhousing 22 which encloses the drive shaft 4 and which-tubular housing isadapted to turn in shifting the lower unit for steering, and forreversing where the devicejis completely turnable. i

matthiastheir. cooling will slightly f cndensefthese `exhaust'gasesand'assist 1in expelling'them from the expansion chamber. -1 i It willalso be apparent that our construcy#vx k tion makespossible-'thep'rovision ofa rel-'1 atively large expansion chamber andmuler" whereby these `exhaust gases coming from the cylin der lmayexpandthereintobefore disf charging underwater, and inf addltion "w'ehave provided meanslfor waterj acketing this expansion cliamberand incoupling up the water circulating system so tlia1,-tl-1e` waterlirst'passes through' the cylinder' and then through the expansionchamber-jacketwhere" it is drawnfioni thehlottest` part of the acket andconducted' straight through the expansion chamber itself anddischargedfinto the passage formed in the hollow housing, which in turndischarges below normal water level.

Having thus described our invention,what we claim as new and desire tosecure by Let ters Patent is:

l. An outboardmotor having a speed controlling ignition system and adepending drive shaft with a tubular housing surrounding it, a propellercarrying casing mounted on the lower end of the housing, the tubularhousing and the propeller casing having a continuous passage fordlscharglng cyllnder gases below normal water level, and means in thetubular housing above normal water level depending upon the speedcontrol :tor opening the passage to the exhaust.

2. An outboard motor having a speed controlling ignition system andl adepending drive shaft with a single tubular housing surrounding it, asupport in which the tubular housing is freely turnable for steering,`

the housing and the propeller carrying casing having a continuouspassage opening at the rear of the casing below normal water level, anexhaust chamber connected with the motor and with the passage in thehousing above the said support, and means in the ltubular housing belowthe support but above for controlling the speed of the motor, and

means operable in response to the actuation of said speed controllingmeans for relieving against the development of back pressures by theexhaust gases within the motor.

4. In a motor assembly for propelling a vehicle through water, the`combination of a support, a motor mounted thereon, means connected withthe motor for effecting the discharge of exhaust gases underwater, a

'shiftable means for controlling the speed of the motor, and meansoperable in response to the-shifting of said speedcontrolling means forrelieving against the development of back;

pressure bythe exhaust gases within the mo- 5. In a motor assemblyfor'vpropelling av vehicle through water, the combinationfwithj asupport', a motormounted thereon, means connected with the motor foreffecting the 1 discharge of exhaust gases underwater,

meansfor controlling the speed of the motor-,f Y

and a valve operatively i associated with the means for el'ectin'g thedischarge of exhaust' gases iunderwater, said -valve being operable 1nresponse to the-,actuationvof the speed cong trolling means for efectinglthe discharge of l exhaust gaseslinto theatrnosphere to relieve againstthe development of'back said gases within'themoton` 6. Inra motorassembly for propellinga vehicle through water, the 'combination :cfasupport, a motormounted thereon, means connected wlththe motor forelfeeting the dis'- charge of exhaust gases underwater, said meansconstituting a casing having a passageway, and a relief kmechanismassociated with said casing which is operable in responseto theactuation of the speedcontrolling means for` establishing communicationbetween the passageway 'within the casing' and the atmosphere to relieveagainstthe devel back pressure by the exhaust gasesy i 7; b inationof asupport, a motor mountedthere# on, means connected with the motor foreffect'- pressure by In an outboard? motor assembly, the comi-H 1 ittingthe discharge ofi exhaust gases underl' water, Ameans for'.controlling ,the speed of the motor5-and1means' operable in responseA tothe actuation of saidspeed controlling means for' relieving against'thedevelopment of back, pressures by the exhaust gases within the* motor,when said' speed controlling means is' the speed of the motor. Y Y

positionedfso as to eect'theretard'ation of 8; In an outboard motorassembly, the com-A binationof a support,a` motor mounted thereon havingan ignition system, means ctmnected withl the motorfor effecting thedischarge ofxhaust gases underwater, shiftable means for controllingsaid ignition system,Y` and means operable inresponse to the actuationof said Lshiftablef:ignition control means yfor re`` lieving againstthedevelopment of back presj sureuby exhaust gases within the motor;

9." l-nani outboard motorassembly, the com# bination of'a support, amotor mounted'thereon,me'ansconnected with the motor foreff `fectingthedischarge ofexhaust gases under` water,'meansi for controlling thespeed of the 1|? motor, alrelief .valveassociated'witlr saiddj meansfor` dischargingtheexhaust gases un derwater, and a leverage mechanismlintere'. posed between the relief valve and the-speed controllingmeans, whereby said relief valve i i combination of a support, a motormounted will be open when. the motor is operating,V at

speedsduringrwhich back pressure of the ex,

haust gases would normally be established, Y 10. In ain outboard. motorassembly, the

vcombination of a support, a motorV mounted.

thereon having ya lower turnable unit lof stream-*line construction,means orfLcontrol-:f ling the speedy of the motor, said unltbeing '1'provided with an anti-cavitation plate, and.

means for effecting the discharge of exhaust gases at a point beneathand at the rearward portionV of said anti-cavitation plate,where.-,;

Vaus

`pressure vof exhaust;l

by said; gases maybe effectively disposedof beneath the surface of thewater and means I depending upon the operation of. said speed foreffecting the discharffe of exhaust gases at f apoint beneath andadbjacent the rearward portion of said anti-cavitation plate, wherebysaid gases maybe electively disposed of beneath thesurface of the water,means for controllingthe speed of the motor, and means responsive to theactuation of said speed controlling means for relieving against thedevelopment of back pressures within the motor when said motor isoperating at speeds during which back pressure of said gasesl wouldnormally be established.

In witness whereof, we have hereunder names.-

LOUIS J. JOHNSON. HARRY L. JOHNSON subscribed our wardly of thepropeller and immediately be-` neath theplate of the anti.cavitationplate,

.whereby exhaustgases may be eeetively dis-1' charged lbeneath thesurface of the water, and an exhaust back pressurerelief above theVanticavitation plate dependent for operav tionlupo'n thespeedcontrolling: means* Y v12. Inl an outboard motor (assembly, the

thereon having a lower turnable unit of stream-line cross section, meansconnected withY the motor for effecting the discharge of exhaust gasesrearwardly of said lowerunit,

. means for controlling thespeed of the motor, and `means operable inresponse to the actuation of said speed controlling means for relievingagainst the development of back pressure by the exhaust,v gases withinthe, motor. Y Y v 13. In an outboardmotor assembly, the combination of asupport-,akmotor rotatably mounted thereon, means connected with themotor for'lefleeting the discharge of .exhaust i 4gases underwater,means for controlling'the speed' of the motor, andmeans operable 4inresponse'to the actuation of said speed controlling means for relievingagainst thedevelopment of back pressures by the exhaust -gases withinthe motor. Y Y

'14. In anioutboard motor assembly, the

combination of'a support, a motor mounted thereon .having -a lowerturnable unit ofl stream-line cross section, said unit being providedwith an anti-cavitation plate, means 'Y

